Carbon monoxide (CO) is an invisible, odorless, colorless gas created when fossil fuels (such as gasoline, wood, coal, propane, oil, and methane) burn incompletely. In the home, heating and cooking equipment are possible sources of CO. Vehicles or generators running in an attached garage could also produce dangerous levels of CO. However, consumers can protect themselves against CO poisoning by installing CO alarms inside their homes; by properly installing, using, venting, and maintaining heating and cooking equipment; and by being cautious with vehicles or generators in attached garages.

Install Carbon Monoxide alarms inside your home to provide early warning of accumulating Carbon Monoxide. However, a Carbon Monoxide alarm is no substitute for safe practices. The best defenses against Carbon Monoxide poisoning are safe use of vehicles (particularly in attached garages) and proper installation, use, venting and maintenance of household cooking and heating equipment.

Household Carbon Monoxide alarms measure how much Carbon Monoxide has accumulated. Currently, Carbon Monoxide alarms sound when the concentration of Carbon Monoxide in the air corresponds to 10% COHb level in the blood. Since 10% COHb is at the very low end of Carbon Monoxide poisoning, the alarm may sound before people feel particularly sick. Most Carbon Monoxide alarms now have silence/reset buttons and must be immune to elevated ambient levels such as those found in urban areas.

Pollution and atmospheric conditions in some areas cause low levels of CO to be present for long periods of time. In fact, these "background" conditions may increase Carbon Monoxide (CO) to over the 10% COHb equivalency level, causing older CO alarms to sound even though conditions inside the home are not truly hazardous. However, newer alarms have been designed to reduce sensitivities to compensate for these background conditions. Treat all CO alarm warning sounds as real, until it has been verified that there is no threat from equipment inside the dwelling.